Agricultural machine



June 29, 1954 L. A. MARIHART AGRICULTURAL MACHINE 4 Shuts-Sheet 1 Filed May 14, 1948 INVENTOR. [m 4 Mar/ham A TTOE/VE Y5 June 29, 1954 A. MARIHART AGRICULTURAL MACHINE 4 Sheets-Sheet 2 Filed May 14, 1948 Ill Fll5 l: FIE E INVENTOR. [e0 4. Mar/barf June 1954 L. A. MARIHART AGRICULTURAL MACHINE 4 Sheets-Sheet 4 Filed May 14, 1948 INVENTOR. Zea A, Mar/barf W Patented June 29, 1954 AGRICULTURAL MACHINE Leo A. Marihart, Monterey County, Calif., as-

signor to M. P. H. Industries, Palo Alto, Calif., a corporation of California Application May 14, 1948, Serial No. 27,090

Claims. 1

This invention relates generally to agricultural machines for the treatment of various plants, and particularly to machines for such operations as fertilizing, spraying and weed control.

In the care or culture of field plants it is common to apply fertilizers and other soil treatment chemicals relatively indiscriminately. For example where the plants are grown in straight rows, it is common to apply nitrates, phosphates, potash and other chemical fertilizers or plant conditioners by the use of a hollow or trough-like shoe which is supplied with a continuous stream of fertilizer, and which is moved along a plant bed through the upper surface of the soil, thereby leaving a continuous line of fertilizer in close proximity with the plant row, and which is subsequently dissolved by water. This method is selective to the extent that the fertilizer is not applied over the entire ground surface, but it does not discriminate with respect to location of plants in the row. It is Well known that only the fertilizer deposited in close proximity with a plant is effective in promoting its growth, and assuming that the plants are spaced from to 24- inches or more apart, which is generally the case, it is evident that a large amount of the fertilizer is not effectively applied. A considerable part of the fertilizer applied in this fashion is ultimately dissipated by rain or irrigation Water, and is therefore largely wasted.

With respect to conventional practice in applying liquid or powdered sprays (e. g. insecticidal or plant treatment sprays) to field plants, it is known that in many instances the spray is most effectively applied when directed downwardly from a region above the plant. Assuming again that the plants are in rows spaced apart a considerable distance, it is customary practice to traverse the rows with continuously discharging nozzles, whereby a considerable part of the spray is not effectively applied to the plants but is discharged upon the ground and Wasted. In some instances the spray may not only be wasted in this manner, but also may be detrimental to the soil.

In recent years several chemicals and chemical compounds and mixtures have been developed for the purpose of killing or controlling growth of weeds and like vegetation other than the desired plant. When such sprays are effectively applied there may be a considerable saving, particularly in that elimination or control of the Weeds may make it unnecessary to carry out more expensive weed eradicating operations. If such spray materials are discharged continuously from spray nozzles, arranged to operate between the rows of plants, then care must be taken not to extend the area of application of the spray to the plants themselves. Therefore the spray is not applied to weeds which may be growing in areas between the plants. Selective application of such sprays manually is not feasible, because of the high labor costs involved.

It is an object of the present invention to provide a machine and method capable of automatically carrying out the operations described above with a high degree of selectively.

Another object of the invention is to provide a machine and method of the above character which is capable of effecting great economies in such agricultural operations as fertilizing, application of spray materials, application of weed eradicators, etc.

Additional objects of the invention will appear from the following description in which the preferred embodiment has been set forth in detail in conjunction with the accompanying drawing.

Referring to the drawing:

Figure 1 is a side elevational View illustrating a complete equipment of the type utilizing the present invention.

Figure 2 is a circuit diagram illustrating a modification of the equipment shown in Figure 1.

Figure 3 is a side elevational view illustrating a photoelectric tube unit such as is utilized in conjunction with the invention.

Figure 4 is another view of the unit shown in Figure 3, but in cross section, illustrating the arrangement of parts within the box.

Figure 5 is a crosssectional view taken along the line 55 of Figure 4.

Figure 6 is a cross-sectional detail taken along the line 66 of Figure 4.

Figure "I is a circuit diagram illustrating a suit able electronic network for coupling to the photoelectric tubes, and for effecting electric control of the timing device.

Figure 8 is a side elevational View showing a tractor equipped with the present invention, and illustrating particularly the photoelectric unit, and means for applying fertilizer and for applying spray materials.

Figure 9 is an enlarged cross-sectional detail taken along the line 9-9 of Figure 8.

Figure 10 is an enlarged cross-sectional detail takent along the line Ill-l0 of Figure 8.

The invention can best be explained after describin the diagrammatic Figure l. A photoelectric unit Ni includes the photoelectric tube H, and the lamp l2. Tube ll connects to the input of an eiectronic amplifier (3, which in turn has output coupled to the input of the power amplifier i l. The output of the amplifier i4 connects to the relay i5, which in turn serves to control the solenoid it of the timing device l. The timing device i? serves in turn to effect timed operation of the fertilizer applying device it, and the spray applying device l9 and the dusting appliance The fertilizer applying device |8 may vary as to details but in this instance it is illustrated as comprising a hopper 2| adapted to contain various fertilizer materials in powdered form, and arranged to feed the material downwardly through pipe 22, control valve 23, and discharge spout 24. In a typical instance spout 24 can discharge the fertilizer over an area adjacent to the plants, or as will be presently explained, a suitable shoe can be employed to deposit the fertilizer into the upper layer of soil adjacent the plants. Valve 23 is adapted to be operated by the electric solenoid 26.

The spray device H? has been shown diagrammatically as comprising simply a pipe 21 provided with the spray nozzle 28, and controlled by valve 29. Electrical solenoid 3| serves to operate the valve 29. Pipe 21 leads to a suitable tank for liquid spray material under pressure.

Device 26 has been shown diagrammatically as comprising the conduit 32 having a downwardly directed discharge nozzle 33, and controlled by valve 34. Solenoid 36 serves to operate the valve 34. Pipe 32 connects with a source of air under pressure together with suitable powder feeding means. 34 powder, such as a suitable insecticide, or fungicide, is discharged downwardly upon the plants.

The timing device I I can be of the type disclosed in my Patent No. 2,437,168, granted March 2, 1948. Briefly this type of timing device comprises a continuously rotating wheel or pulley 3?, having its periphery frictionally engaged by the elements 38. Elements 38 may be small magnetic members frictionally retained to the periphery of the wheels 31 by magnetic attraction, or as disclosed in said patent they may be made in such a manner as to have frictional engagement with the wheel. Normally a plurality of elements 38 are retained in single file upon the wheel 3'! i by the releasable star wheel 39. A suitable trigger arrangement, controlled by solenoid I6, is provided for retaining star wheel 39 stationary. Upon releasing the trigger means star wheel 39 is permitted to rotate a sufficient distance to release one of the elements 38. The released element then moves on the wheel 31, until it takes a position at the end of the row of elements.

In order to minimize the possibility of false operation, the relay I5 is preferably of the type having a holding circuit and a pair of holding contacts, and used in conjunction with the release switch 4|. Thus the magnet of the relay i5 is provided with two coils 42 and 43, the former being connected to the output of the amplifier I4, and the latter being included in the holding circuit 44. Movable and stationary relay contacts 45 and 4! are connected in series with circuit 44, and this circuit also includes the battery 48 or other source of current, and the switch 4|. Thus when winding 42 is energized the contacts 46 and 4'; are closed to supply holding current to the winding 43, and this holding circuit remains closed until operation of the switch 4|. The main movable and stationary contacts 43 and Upon opening valve 5| of the relay are included in a circuit for energizing the solenoid l6. Thus one side of this solenoid is shown connected to ground and the other side connected to the movable contact 49. Stationary contact 5| is connected by conductor 52 to one side of the condenser 53, and the other side of this condenser is connected to ground. A resistor 54 connects between conductor 52 and a source of condenser charging current. When contacts 49 and 5| are opened condenser 53 is charged by current supply to resistor 54. When the contacts 49 and 5| are closed the condenser discharges through the solenoid |6, thus operating this solenoid to release the star wheel 39. Closing of contacts 49 and 5| is accompanied by closing of the contacts 46 and 41, to close the holding circuit 44, and as a result the relay contacts remain closed until a released element 38 operates the switch 4|, at which time the opening of the holding circuit 44 permits the relay contacts to open.

In order to exclude the effect of daylight or other extraneous illumination, I make use of a pulsating source of light together with a tuned or selective amplifier system. Thus the lamp I2 is preferably of the gas discharge fluorescent type, and is excited with the pulsating current at a definite frequency of say 115 pulsations per second. The so-called daylight type of tube has given good results. The current supply source for this lamp has been shown including the pulsator or vibrator 56, together with the transformer 51. The pulsator or alternating current thus applied to the lamp l2 serves to produce pulsating illumination. The photoelectric cell or tube is receptive to light produced by the lamp l2 and reflected back from a plant, and the amplifiers l3 and M are selectively tuned to amplify pulsations only such as are produced by the light source, which for the lamp exciting current frequency of 115 cycles per second, will be 230 cycles per second.

A suitable type of photoelectric unit is illustrated in Figures 3 to 6 inclusive. Briefly it consists of a box-like housing 6| having a removable top cover 62, and a transparent bottom plate or wall 63 preferably made of glass. The glass wall is secured to the sides of the box by means of the side retaining clamps 64. Within the box and between the photoelectric tube H and lamp l2 there is a partition wall 56, which extends downwardly to a point substantially in contact with the inner face of the plate 63. On one side of the partition 65, and extending between the lamp l2 and the glass wall 63, there is a slot or elongated space 61 through which light is transmitted from the lamp. Upon the other side of the partition 56, means is provided for collecting reflected light and for applying it to the photoelectric tube N. This means consists of a relatively fiat lens 69 made of suitable material. such as a transparrent plastic, and having upper and lower arcuately curved edges H and 12. This lens is retained within a suitable opaque housing which includes the metal plates 13 and 14, and the metal shroud 76 for the photoelectric tube The lower edges of plates 13 and I4 terminate in contact with the inner face of the glass wall 63 as illustrated in Figure 4. The lens 69 collects light from a space H which is substantially coextensive to the length of slot 61 (see Figure 6) and serves to concentrate the collected light upon the relatively shorter photoelectric tube A suitable light filter 15 is shown positioned between tube and the lens 69.

From Figure 4 it will be noted that light being transmitted downwardly through the glass plate from the lamp I2 is directed substantially at right angles to the plane of the plate. Therefore a portion of a plant caused to occupy the zone indicated at I0, extending coextensivewith the length of slot 61, is illuminated, and light reflected from this plant portion is caused to be reflected back through the glass plate and to be collected by the lens 69, for application to the photoelectric tube II. Lens 69 is disposed at a substantial angle to the glass plate, as for example at an angle of approximately 45 as illustrated, so that the majority of light reflected from the surface of the glass plate 63 is not collected and applied to the photoelectric tube. Line BI in Figure 4 represents the ground surface, and the movement of the unit is preferably from right to left. Assuming application to relatively small plants, the device is arranged to pass over the row of plants in such a manner that the plants are bent over and caused to pass beneath the plate 63. Light is therefore reflected from the bent over stem portions or the lower leaves of the plants, for eifecting a light response of the photoelectric tube I i. Foliage continually wipes over the lower surface of the plate 63, thus keeping it relatively free of dust.

Various arrangements can be used for mounting the photoelectric unit on a tractor or like vehicle for movement along a row of plants. Preferably it is mounted in advance of fertilizing, and plant spray or dusting devices. One suitable arrangement is illustrated in Figure 8. A motor powered tractor or like vehicle 32 is provided with a frame 83, carried by the small wheel 84. Parallel links 85 and 86 attach the frame 83 to the mounting bracket 81 attached to the tractor frame. A lever arm 88 is fixed with respect to link 86, and connects with an operating rod 83 which extends to the rear of the tractor, where it slidably extends through the collar 9| carried by arm 92. Arm 92 connects with a hydraulic operator provided on the tractor. Adjustable collars 23 and M are fixed to the rod 85!, whereby when lever 92 is swung to the left, rod 89 is moved to the left to raise the frame '83. A countel-balancing compression spring 96 surrounds the rod 82, and has its one end seated upon the shoulder 9'1 and its other end on the collar 22. The position of collar 98 can be adjusted by changing the setting of the hand lever 99. Thus a desired amount of spring force can be yieldably applied to lever 88, in a direction to counterbalance the weight of frame 33 and parts carried by the same.

A structural member hill is pivotally attached at I02 to the frame 83. The photoelectric unit III is carried by member ill! and frame 83, preferably in such a manner as to permit its independent vertical movement. Thus a pair of spaced parallel bars Hi3 extend vertically on opposite sides of the member Iill, and the lower ends of these bars are attached to a yoke ISM, which embraces the photoelectric unit Iii. The lower ends of the yoke are attached by studs H36 to the clamp brackets 64 of the photoelectric unit. A bracket I01 carried by the frame 83 serves to pivotally mount a pair of levers I53. These levers are connected to the bars 33 by the, cross connected links I03. With this arrangement the bars H33, together with the photoelectric unit Ill, move in a rectilinear and vertical direction to accommodate for variations in ground level. If desired a suitable counterbalance spring can be applied between bars I03 and the member IBI, to

offset in part the weight of the photoelectric unit and associated parts. Also it is desirable to provide a small ground engaging runner or shoe III mounted upon the photoelectric unit (see Figure 3) in order to maintain the same at a substantially constant distance from the ground surface.

The various plant treating devices I8, I9 and 20 described generally with'reference to Figure 1, can all be suitably carried by the frame of the tractor and preferably mounted upon the member IEII. Figure 8 illustrates a modified type of fertilizing device I I2, and more elaborate applying devices H3 and II4. Device II2 makes use of a hollow runner or shoe I I5 which is attached to the lower end of rod II6. This rod is adjustably carried by the bracket II I, which in turn is mounted upon member NH. The interior of the shoe connects with a pipe or hose H8, and which may for example be an extension of the pipe 22 of Figure 1. The rear end of the shoe I I5 is open for the discharge of fertilizer. Figure 10 illustrates how the shoe operates through the ground whereby powdered fertilizer is discharged into a trough formed in the ground. This trough may be relatively close to the plant row.

Device I I3 (Figure 9) consists of a simple frame I2! attached to bracket I I! and serving to mount the liquid spray nozzles I22. These nozzles connect to a common pipe I23, which may correspond for example to the pipe 27 of Figure 1. Flexible cloth curtains I24 are draped from frame I2I to enclose a spray applying space.

Device H4 is for application of powdered materials and may consist of a frame I20 attached to bracket II! and from which curtains I25 are draped to enclose a dusting zone. Pipe 33 (Figure 1) communicates with the space enclosed by the curtains.

Referring back to Figure 1, means is employed in conjunction with the timer I! for effecting automatic and properly timed operation of the devices I3, I9 and 20, or devices H2, H3 and H4 of Figure 8, responsive to a light indication secured from a plant by the photoelectric unit I0. Thus the timer is provided with switches I26, I27 and I28, serving to control respectively the operation of solenoids 26, 3i and 36. One terminal of each of the switches I26, I21 and I28 is shown connected to a common conductor I29, which in turn connects to the battery I3I or other source of current, and thence to ground. One side of solenoid 26 is connected to ground, and the other side is connected through switch I32 to the timer switch I26. Solenoid 3I has one side connected to ground and the other side connected through switch I33 to the timer switch I 27. Solenoid 36 has one side connected to ground and the other side connected through switch I34 to the timer switch I28.

All of the timer switches can be of the type having snap action of their contacts, and actuated by relatively small movement of an operating member. The operating members E35, I3! and I38 for the switches I26, I27 and i 23 are indicated as extended wires bent laterally at their ends in order to prolong engagement with the element 38.

It will be evident that when an element 38 is released to travel with the rotating wheel 31, it will first effect operation of switch ii, and then successively engage the operating elements of the other switches. The time period during which each switch is operated will depend in part upon the time period of contact with the element 33, and this can be controlled by the length of the operating element provided for the switch. It will be evident from Figure 1 that when an element 38 is released by receipt of a light response from the photoelectric unit 10, this element will successively operate switches l26, I27 and l2%, and in each. instance the time interval from the instant of actuation by the photoelectric unit until operation of that particular switch (assuming constant speed of rotation of wheel 3?), will depend upon the positioning of the switch about the wheel 3'5. As disclosed in said Patent No. 2,437,168, this positioning can be adjusted as desired.

In order to more efiectively control the period during which each solenoid 28-, ill or 36 is energized in response to a given light actuation, it is possible to use the more elaborate arrangement of Figure 2. Each of the switches 26, L21 and i28 (in this instance switch 523 only is shown) can be supplemented by an extra switch iZfla, to control a holding circuit for the relay Ml. Relay SM is provided with a winding iii connected to the energizing circuit Hi2, which is controlled the main switch 28. The switch itfla is included a holding circuit i 5 which comprises the holding winding iii-G, the movable and stationary relay contacts M? and Mil, and the battery M9. The main relay contacts 155 and 152 are connected in the energizing circuit for the solenoid 36, which includes the switch iiil and the battery 153. It will be evident that closure of switch 28 serves to energize the wind-- ing i 56 and the relay Hi5 to close all of the relay contacts. Closing of the contacts Ml and I63 closes the holding circuit hit for the winding Mt, thus holding all of the contacts closed. Subsequently upon operation of switch l28a, the holding circuit Hi l is broken, thus permitting the relay contacts to drop open. By changing the position of switch iZda with respect to switch I23 the time period of closure of the relay can be adjusted to a desired value.

It will be evident that other parts of the apparatus which have been indicated diagrammatically in Figure l, are incorporated in the apparatus of Figure 8 and are suitably and conveniently mounted upon the tractor. Such parts as the amplifiers and relays are conveniently mounted upon the tractor within the box ltl. The timer wheel 3? has a drive connection to a portion of the tractor transmission so that it is driven at rate corresponding to the forward movement of the vehicle. The timer can be convenicntly carried within the box or enclosure it i, and can be connected to the transmission of the tractor by means of a suitable flexible drive. Likewise it will be apparent that suitable tanks or bins, together with suitable agitators known to those familiar with spray and dusting equipment, can be mounted upon the tractor to supply the fertilizing, spraying and/or dusting devices.

Operation of the complete apparatus can now be described as follows: The machine is to be used where plants are grown in relatively straight rows, as for example in raised beds with two rows to the bed. The plants will be spaced apart a distance varying in different instances. For example on plants such as lettuce, the spacing may be of the order of from 1o to 14 inches, for sugar beets from 8 to 18 inches, for cotton from 12 to inches. The photoelectric unit it is set to operate at a suitable height above the ground surface, depending upon the particular plant being operated upon, and depending upon the plant size. Where the plants are relatively small the unit can be made to operate fairly close to the ground surface, as illustrated in Figure 8. For the larger plants it is necessary to operate at a greater height from the ground. In any event it is desirable to have unit In arranged whereby in passing over the plant row, the plants are bent over, and a light indicated secured from the bent over stem portions of the plant or the lower leaves which indicate the center of the plant with reasonable accuracy. Upon receipt of a reflected light indication from a plant by the photoelectric unit, the solenoid 16 of the timer is immediately operated, and an element 38 released. This element thereupon moves together with the wheel 31 to effect successive operation of the switches I26, I21 and I28. Upon operation of switch I26 the solenoid 25 is energized for a short interval to open valve 23, and thus to discharge a given quantity of powdered fertilizer upon the ground surface adjacent the plant. Assuming that one uses the shoe H5 of Figure 8, then a quantity of the fertilizer is applied adjacent the plant and in the trough formed by the shoe. The time delay between receipt of the response and operation of the solenoid 26 is determined by timer El and is such that the fertilizer is applied in close proximity to the same plant which caused the response. Operation of the switch i2! causes actuation of solenoid 3! to dischar e a liquid spray from the nozzle 28. Here again the time interval following the receipt of the light response is such that when the spray is applied the same plant which caused the light response is within the curtains lZ i. Operation of switch 123 similarly causes energizing of solenoid 3G with the result that a powdered material, such as an in secticide or fungicide, is discharged upon the same plant.

It will be evident from the foregoing that my machine is capable of wide usefulness for various agricultural operations on plants, and is susceptible to many modifications and variations to suit different requirements. For example with respect to liquid spray materials it is evident that liquids having insecticidal properties can be used, as well as liquids having substances which affect the plant growth or its life cycle, including such substances as plant hormones, chemicals for controlling diseases such as chlorosis, and the like. In addition to using a liquid spray directly upon the plants it is possible to use one or more spray nozzles arranged to discharge liquid spray upon Weeds growing around and between the plants. The liquid supplied to such nozzles can likewise be controlled automatically from the photoelectric unit Hi, whereby such weed control sprays can be applied between the plants as well as alongside of the same, thus eradicating weeds which otherwise would require removal by cultivation. In this instance control from the photoelectric unit serves to shut off discharge of the spray, to prevent its application to the plants. In many instances it may not be desirable or necessary to carry out more than one plant treatment operation under the control of the photoelectric unit. For example the machine may be used for selective fertilizer applications, without application of any sprays or insecticides. Likewise it is possible to apply liquid spray or powdered material without any fertilizmg.

It will be evident that the use of my machine makes possible important economies in the use of fertilizers, sprays, insecticides, and other ma- 9 terials which can be selectively applied. Because of the economies effected greater care can be exercised to provide for fully adequate application.

Previous references has been made to the special amplifiers I3 and I4, together with the relay I5, which secure responses resulting from the reflection of light from lamp I2, while at the same time the apparatus is immune to daylight and extraneous sources of light. It is suitable for this purpose to utilize the circuit illustrated in Figure 7, and which is disclosed in Patent No. 2,596,591.

The amplifying means in this instance includes the cascade connected vacuum tubes I16 and I11. The particular tubes illustrated are of the triple gridamplifier type, such as tubes known by manufacturers specifications as No. 6SJ'1 or 6AC7W. Resistance coupling is provided between the photoelectric tube and the input of tube I16. Conductor I10 is connected to one side of the photoelectric tube I I,. and is grounded. Conductor I19 connects the other side of the photoelectric tube (the anode) to the grid I82, in series with the coupling condenser I84. Coupling resistor I86 connects across conductors I10, I19 and a leak resistor I81 connects between condenser I18 and the grid I82. The cathode I83 and the grid I8I are connected to ground through the biasing resistor I80. The anode I89 of tube I16 is connected in series with the resistor I9I to the conductor I92, which in turn is connected to a source of plate supply voltage through the resistor I93. In a typical instance the voltage of the plate supply can be of the order of 350 volts.

Conductor I92 connects to ground through the series connected voltage regulating tubes I94, I95. These tubes can be of the type known by manufacturers specifications as VR150. Voltages are applied to the anode of the tube I16 by means of the resistors I96 and I91, which function as a filter in conjunction with condenser I08, and as a voltage divider in conjunction with resistor I86.

The second grid I99 of tube I16 is connected to ground through the by-pass condenser MI, and is also connected to conductor I92 through the resistor 202, whereby suitable voltage is maintained upon the grid.

The vacuum tube I11 has its grid 203 connected to an adjustable tap on resistor 204, which in turn has its one end grounded, and its other end connected to the plate I89 of tube I16 through the series coupling condenser 206. Adjusting the setting of the tap on resistor 204 serves as a sensitivity adjustment. The grid screen 201 of tube I11 connects with the cathode 208, and thence to ground through the resistor 209. Grid 2 connects to ground through the by-pass condenser 210,. and to the conductor I92 through the resistor 2 I 2, whereby suitable voltage is maintained upon the grid with respect to the potential maintained on the cathode. The plate 2I3 of tube I11 is connected by the conductor I92 to a suitable tuned circuit 2I4 consisting in this instance of the inductance 2I6 and shunt capacitance 2I1. This circuit is tuned to the frequency of the light source whereby the amplifying system is responsive only to pulsations of substantially the same frequency.

Condenser 2I8 serves to couple the plate 2I3 of tube I11 to the grid 2I9 of another vacuum tube 22 I. This tube can be of the thyratron type such as a three element tube known by manufacturers specifications as No. 884 or a tube of the shielded grid type known as No. 2050. The cathode 222 of thyratron 22I is grounded as indicated, and the grid is connected to a suitable source of negative bias through the series resistors 223, 224. Condensers 226, 221 are shown connected from the negative bias to ground, and from the mid-connection between resistors 223, 224 and ground.

In conjunction with the thyratron 222i, and taking the place of the relay I5 of Figure 1, there is a relay 228 provided with two sets of contacts I, 2 and 3, 4. The stationary contact 2 connects to the plate 229 of thyratron 22I.

- is grounded.

The cooperating movable contact I is connected by conductor 23I and the series resistor 232 to the grid 233 of another vacuum tube 234. This latter tube can be of the triode amplifier type such as a tube known by manufacturers specifications as No. 6J5. The plate 236 of this tube is connected by conductor 231 to a suitable source of plate battery potential, such as a potential oi the order of 250 volts. A cathode 238 is connected by conductor 230 to one terminal of the coil 24I of relay 220. The other side of this coil connects to the stationary contact 4. Grid 230 is also connected to ground through the resistor 242.

The release coil I6 oi the timer has its one terminal connected by conductor 202 to the conductor 213i, and thus to the movable contact I, and its other terminal connected by conductor 263 to one side of a current supply condenser 264. The other side of this condenser Conductor 263 also connects to conductor 231 through the resistor 266. Switch II, which in this instance is normally open, has its one side grounded and its other side connected by conductor 261 to the stationary contact 4 of the relay. In addition this conductor is connected to one side of a simple push-button or switch 268, the other side of which is grounded. A single switch 269 has been shown in this case for controlling a circuit including the solenoid 211 for operating the spray application valve 212. One terminal of solenoid 211 is connected to switch 260 and to ground, and the other side is connected by conductor 213 to the conductor 231 and to the plate current supply of tube 234, through the series resistor 214. Also conductor 213 is connected to one side of the current supply condenser 216, the other side of which is grounded. A small signal or indicator lamp 211 of the neon or glow-discharge type is shown connected between conductor 262 and ground, in series with the resistor 218.

Assuming operation of the amplifier system described above at a frequency of the order of 230 cycles per second, the various resistors and condensers included in the network may have values as follows: Resistors I80, 181', I96 I91, 2 megohms; resistor I60, 1200 ohms; resistor I93, 1500 ohms; condenser I26, 20 mid; resistor I 9|, 220,000 ohms; condensers I04 and 206, 0.01 mfd.; condenser 20I, 20 mid; resistors 202 and 204, l megohm; resistor 206, 500 ohms; condenser 2H), 20 mid.; resistor 212, 150,000 ohms; resistor 223, 100,000 ohms; resistor 224, 10,000 ohms; condenser 226, 0.25 mid; condenser 221, 0.025 mid; condenser 210, 0.01 mid; condenser 264, 20 mid; resistor 266, 5,000 ohms; resistor 214, 5,000 ohms; resistor 232, 150,000 ohms; resistor 242, 200,000 ohms; condenser 21%, 30 mid; and resistor 218, 100,000 ohms.

Operation of the amplifier system shown in Figure '7 is as follows: Lamp 12 is started in operation by the use of a suitable starting arrangement, and switch 280 is then momentarily manually closed, and the coil 24! energized by current supply from the cathode of the tube 234. Closing of the contacts of this relay causes the relay to be locked closed because the closing of contacts .3 and 4 completes the holding circuit to ground through the coil 24!. The grid 259 of the thyratron 22l is biased at this time in such a manner that the plate to cathode impedance is relatively high. The plate current source connected to conductor 23'! charges condenser 264 through resistor 25B, and also charges condenser 216 through resistor 2M. As long as condenser 254 is charged the small neon indicator lamp 211 is illuminated. Assuming now that a plant passes beneath the glass plate of the photoelectric unit, it causes a reflected light indication to fall upon the photoelectric tube, whereby pulses of a frequency corresponding to the frequency of the light are applied to the input of the amplifier tube [76, and amplified pulses are impressed upon the input of the ainplifier tube Hi. The amplification system is responsive only to pulses of the light frequency because of the action of the resonant circuit 2 l4. When tube ET! receives amplified pulses plate 1H3 assumes a potential differing from the potential of the thyratron grid 25d, and therefore the potential of the thyratron grid is changed whereby the thyratron is fired, or in other words, the plate to cathode impedance is reduced to a relatively low value. When this occurs the condenser 254 discharges through a circuit including the timer coil It, relay contacts I and 2, and the plate to cathode path of the thyratron, to efifect release of the star wheel of the timer to thereby release one of the elements 38. Discharge of the condenser 26s as described causes the lamp Ell to be extinguished.

Simultaneously with the discharge of condenser 26 8 the potential of conductor 23! and grid 233 of tube 234 is reduced from the relatively high positive value of the order of say 209 volts, to a relatively low Value. This serves to block the plate current of tube 234, or in other words, to provide a relatively high plate to cathode impedance. As a result fiow of holding current to the relay coil 24! is interrupted or reduced to a relatively low value, whereby the contacts of the relay are released. Release of the relay renders the network inoperative insofar as further pulses from the photoelectric tube are concerned. Upon release of the relay 228 the opening of contacts I, 2 permits the grid 23?, of tube 234 to again resume a rela tively high positive value with the result that the plate to cathode impedance of this tube is again made relatively low.

When the released element 38 has traveled sufficiently far to operate the switch 4|, closing of this switch establishes a current flow through coil 2 1i of the relay, with the result that the relay is again closed to cause the apparatus to be conditioned to receive another light response. When the released element reaches the operating switch 269, its circuit is closed which includes solenoid 2H and the condenser 21%, whereby this condenser discharges through the solenoid to open the valve 272. Immediately upon discharge of the condensers 254 and 216 in the manner described above, they are recharged by current supply from the plate current supply connected to conductor 231.

This application is a continuation-in-part of subject matter disclosed in my co-pending application Serial No. 567,852, filed December 12, 1944, now Patent No. 2,502,468, and entitled Agricultural Machine and Apparatus.

I claim:

1. In an agricultural machine of the character described, a frame adapted to be moved along a plant row, a photoelectric unit carried by the frame and adapted to be moved in proximity with the plants of the row, whereby light indications are secured by said unit from the individual plants of the row, means carried by said frame for selectively applying insecticidal material to the plants of the row, means including a timing device controlled by said photoelectric unit and serving to effect selective timed operation of said last named means.

2. In an agricultural machine, a frame, a photoelectric unit carried by the frame and adapted to traverse the plant row in proximity with the plants, said unit serving to receive light indications from individual plants of the row, means carried by said frame a fixed distance behind said unit and serving to apply fertilizer to the plants of the row, and means including a timing device controlled by said photoelectric unit and serving to effect selective operation of said fertilizer applying means, whereby fertilizer is selectively applied only to regions adjacent the plants.

3. In an agricultural machine of the character described, a frame adapted to be moved along a row of plants, a photoelectric unit carried by the frame and adapted to be moved along a plant row in proximity with the plants, said unit receiving light responess from the individual plants, powder dusting means carried by the frame behind said photoelectric unit, and means including a timing device controlled by said photoelectric unit and serving to effect selective timed operation of said plant dusting means to effect selective application of powder to individual plants.

4. In agricultural apparatus of the character described, a photoelectric unit, means for movin the unit in close proximity with a plant row whereby the unit receives light indications from the individual plants in the row, means moving along the plant row a fixed distance behind said photoelectric unit adapted to be controlled to apply material to the individual plants, a timing device controlled by said photoelectric unit, and means controlled by said timing device for causing selective operation of said second named means.

5. An agricultural apparatus of the character described, a photoelectric unit, means for moving the unit in close proximity with a plant row whereby the unit receives successive light indications from the individual plants in the row, at least two appliances moving along the plant row at different fixed distances behind said photoelectric unit, each of said appliances being adapted to be controlled to selectively apply material to the individual plants, a timing device controlled by said photoelectric unit, means controlled by said timing device for causing selective operation of one of said appliances to thereby selectively apply material to the individual plants, and means controlled by said timing device for causing selective operation of the other appliance to thereby apply material to the individual plants, said timing device including means serving to effect operation of means for operating the appliances in sequential order on successive plants of the row.

References Cited in the file of this patent;

UNITED STATES PATENTS Number Name Date Evans Oct. 11, 1898 Harden July 23, 1912 Moench Jan. 8, 1918 m Saladiner Sept. 28, 1929 Saladiner June 21, 1921 Wood Dec. 19, 1922 Oldham Aug. 21, 1923 Peel Dec. 21, 1926 15 Thompson Sept. 10, 1929 Geffs Mar. 9, 1937 Ferte Oct. 31, 1939 Mather Apr. 15, 1941 Number Number Name Date Thompson Aug. 5, 1941 Nelson July 14, 1942 Marihart May 21, 1946 Wolfner June 4, 1946 Hurley Dec. 30, 1947 Marihart Apr. 4, 1950 Hamilton Aug. 29, 1950 Packard May 13, 1952 FOREIGN PATENTS Country Date Great Britain of 1902 Great Britain July 9, 1947 OTHER REFERENCES Seymour: The Garden Encyclopedia, published 1939 by Wm. H. Wise & 00., N. Y., pp. 393, 394, 395, 459 through 463, 1119 through 1124. 

